A vehicle (hereinafter will be referred to as electric vehicle) which uses electric energy as a driving power source incorporates electric components such as a battery storing DC power, an inverter which converts the DC power stored in the battery into AC power, and an electric motor activated by the AC power output from the inverter. These electric components are accommodated in a case having an insulativity to be isolated (floating) from a vehicle body ground location maintained at a ground potential. For example, Patent Literature 1 discloses that a ground leakage is detected and a ground leakage location is estimated even in a state in which the battery is isolated from the vehicle body ground location.